When nuclear fuels are reprocessed, fuel solutions are formed during dissolution which can contain undissolved solids having a grain size in the range of 10.sup.-4 mm to 5 mm. It is essential to be able to obtain samples that are representative of these suspensions.
Known sampling devices in reprocessing facilities use a combination of a sealed sample vessel and a hollow needle filling means to transfer the sample of the solution into sample vessels. The filling port of the vessel is sealed by a rubber septum through which one or two hollow needles are inserted; these needles are ground to an acute angle. The vessel is filled through the inserted needles.
When the filled vessel has been pulled off the hollow needle or needles, the resilient rubber septum closes the place of incision. The material is only incised rather than being punched out because of the special grind of the needles and because of the needle diameter of up to about 2.5 mm. Larger needle diameters cannot be used, as they would punch material out of the septum, and the openings formed thereby could not reclose when the needles are withdrawn. Accordingly, suspensions having a maximum particle size of about 2 mm can be filled into vessels as representative samples with the rubber-septum/hollow-needle combination. If there are larger solid particles in the suspension, obstructions will develop or non-representative samples will be obtained.
German published patent application DE-AS 2,614,787 discloses an apparatus for taking radioactive liquid samples and with which a sample can be taken from a radioactive liquid circuit. In this apparatus, the problem of a blockage in the hollow needles by the solid particles of the liquid is said to be solved in that the hollow needles subjected to blockage are arranged and configured so that they can be exchanged far more easily.